Can an adult divorce their family? I know longer want to have any kind
of contact with them

http://www.randomhouse.com/rhpg/catalog/display.pperl?044990590X
Divorcing a Parent by Beverly Engel, M.F.C.C.

No one should have to endure an abusive, unhealthy relationship that
threatens his or her well-being -- even if that relationship is with a
parent. In this ground-breaking book, Beverly Engel draws on her own
personal experience, as well as the stories and letters of other adult
children, to offer a complete guide to why, when and how to divorce a
parent. Engel discusses good and bad reasons for taking this step,
when to stop trying to reconcile, and how to prepare yourself
emotionally for the actual divorce, including such alternatives as
temporary separation. If you do decide that parental divorce; how to
handle negative pressure from others; how to come to terms with your
own grief and guilt; what to tell your own children, and how to deal
with their relationships with their grandparents; how to cope with
holidays; how to divorce a parent after his or her death; and what to
do if you change your mind and want to reconcile.

If you are an adult, then there is no reason to "divorce" your family.
The reason a child would do this is to become emancipated so that they
can legally leave the family home. As an adult you are free to leave
the home and not communicate or associate with your family without any
legal process.  What would you accomplish in this "divorce" that you
could not accomplish without it?

It would be much easier to have a court order tell your family you
don't want to have contact with them. However, part of being an adult
is having the backbone to stand up for yourself and say NO. You can
say NO by not answering phone calls, not participating in family
functions, and most of all, not allowing yourself to get drawn into
the family drama that so distresses you.

For now, distance yourself by demonstrating your unhappiness by
choosing to not participate, at all. In time, things will change, then
you can reevaluate.